The present invention relates to a caster assembly for a use with furniture, and, more particularly, to a caster assembly adapted for use with bed rails or a bed frame including side rails and cross members and which allows the weight on the caster to be centrally positioned and further has a glide that can be easily attached and/or detached from the caster assembly.
In general, bed frames are well known and are comprised of various structural members such as side rails and cross members that interconnect the side rails and provide a relatively rigid structure of predetermined dimensions in order to support a box spring and a mattress. The common side rail member and cross member is an L-shaped steel member with various manners of connecting the individual components together.
The components, that is, the side rails and the cross members also are generally provided with legs that extend downwardly toward the floor so that the components are elevated from the floor and include caster assemblies interfitted to the legs to allow the bed frame and completed bed to be moved to differing locations in the room.
Accordingly, the caster assemblies normally have rotatable rollers to facilitate the movement of the bed from one location to another. Such caster assemblies also generally have an elongated stem that interfits with a corresponding female connector on the bed frame leg. That stem has a central longitudinal axis along which is directed the weight of the components of the completed bed, i.e. the box spring, mattress and the like. The roller itself is mounted to the assembly within a housing and the roller is rotatably mounted to that housing to roll about a central axis that is parallel to the plane of the floor. The housing is also pivotally mounted to the frame leg so that the roller itself can not only rotate about its axis, but the housing, including the roller itself, can also pivot 360 degrees about the main longitudinal axis of the stem.
The swiveling action or movement is necessary to correctly align the roller for movement in the proper direction, however, such swiveling movement can be generally difficult to accomplish. For one reason it is apparent that all of the rollers supporting the bed frame must be correctly aligned in order to easily move the bed frame. In most instances, the rollers are positioned in various directions and it is therefore necessary to align all of the rollers at the initial movement of the bed frame. With the weight of the mattress and box spring there is considerable friction acting against the swiveling action of the caster assembly and the problem is aggravated by the need to align some 4-5 rollers in order to roll the bed frame. Additionally, the roller is often embedded into an indentation in the carpet that lies along the surface of the roller and the roller must be moved out of the indentation to swivel. As such, therefore, while the swivel action is necessary to properly move the bed or other furniture, it can be somewhat difficult to get the swivel action to operate easily and thus the initial movement of the bed is not easy to accomplish, particularly when the bed is on carpeting with padding.
The preferred conventional caster for use with carpet is a cylindrical member that contacts the floor at a certain finite distance away from the longitudinal axis of the stem so that the roller can pivot to a position determined by the direction the frame is being moved and then the roller rotates to make that movement easy to accomplish. A typical roller caster assembly is shown and described in U.S. Pat. No. 4,007,502 of Mis. As can be seen in the Mis patent, the roller is offset with respect to the downward force that acts through a stem and, as will become clear, this typical caster of Mis suffers from certain inherent weaknesses.
Thus, since the contact point between the roller and the floor is located at an offset dimension from the longitudinal axis of the stem along which the weight of the bed is directed, a bending moment is created based on the weight of the bed acting downwardly on the stem and the distance between the location of that force along the longitudinal axis of the stem and the point where the roller contacts the floor to support the frame.
One of the difficulties with such casters, therefore, is that the bending moment created by that offset causes stress on the caster assembly and can cause a premature failure of the caster assembly or the bed frame leg itself, thereby disabling the entire unit. The problem is aggravated, of course, with legs having increased degrees of weakness, and in particular, with the use of plastic legs as shown and described in U.S. Pat. No. 3,828,376 of Miller. Accordingly, it would be advantageous to have a caster assembly that has rollers that provide better support for the bed and which do away with the offset that causes the bending moment and the premature fracture of essential components such as the leg of the bed frame, thus avoid damaging the bed frame. There are rollers that have ball bearings the may aid in the swiveling of the roller or aid in the rolling motion of the roller itself but all require the offset and the consequent swiveling action to operate in moving the furniture.
Other prior art furniture support assemblies have, in fact, utilized a plurality of elements that contact the floor and examples are illustrated in U.S. Pat. No. 1,060,076 of Glowacki and U.S. Pat. No. 1,282,396 of Friend. In the aforementioned patents, however, while a plurality of members contact the floor and thus allow the weight to be borne by a plurality of elements, there is a further problem with respect to the ease of moving such casters as the spherical members are clamped into the housing supporting the particular piece of furniture and the spherical contact members do not thus freely rotate to allow the ready movement of the furniture. Accordingly, in Glowacki, the balls that actually contact the floor are clamped tightly into a circular dome and thus are not movable with respect to the dome as the furniture is moved. Therefore, while the prior art did consider the support of the weight of a piece of furniture on a plurality of contact members, the moving of the furniture was not enhanced and only the idea of a strong support was considered and appreciated.
In addition to caster assemblies, there are also glide assemblies that are mounted to the various frame members and have a generally flat, planar bottom contacting the floor. The glide assemblies are preferably used where the bed is located on a hard or slippery surface such as a wood or tile floor and thus the flat bottom does not easily slip or cause damage to the floor itself. With such flooring surfaces, the user of a caster having a roller causes unnecessary sliding or rolling as contrasted to the intended use of a rug roller or caster on a carpeted surface where the friction with the carpet reduces the mobility of the roller or caster.
In the case of bed rails, typically glides are used to support the center member that spans the width between the side rails. The side rails themselves are connected at their ends to a headboard and a footboard and have one or more center supports having a leg or legs that include a glide that contacts the floor to add strength to the assembly. Since the height of the legs on headboards and footboards is not a standard height, it is necessary for the center support for the cross members be adjustable in height so as to provide proper support from the floor for the cross members. Typical cross members and adjustable glides are shown and described in U.S. Pat. No. 5,894,614 of Stroud. As can be seen in that patent, the cross members contacting the floor are adjustable for height by means of a threaded engagement with the leg of the cross member. With such side rails, however, the use of a glide to support a cross member has certain problems, that is, the strength of a glide is needed, yet there is also needed some mobility so that the bed rail type of bed can be moved from one location within a room to another location. In moving the bed rail type of bed, with a center adjustable glide, the glide can catch on the floor, particularly with a carpet, and thus twist the cross member and cause breaking of the leg itself.
Glide assemblies are inherently stronger that caster assemblies since the weight of the bed frame using a glide acts along the longitudinal axis of the glide directly to the point of contact with the floor, and thus, there is no offset from that axis to the point of contact and, hence, no bending moment. In addition, of course, the glide planar surface allows more surface contact with the floor and thus carries the weight of the bed over a wider area so as to provide a better distribution of that weight. As such, the glide assembly has enhanced strength and stability over the caster assembly.
Accordingly differing ideas have been proposed to solve the problem of the height adjustibility required for a glide supporting a cross member and most of the ideas relate to the mechanism to bring about that adjustment. As examples of the various approaches to make the glide mechanisms adjustable, note Mitchell U.S. Pat. No. 5,815,860 and U.S. Pat. Nos. 5,894,614 and 4,080,674. From those examples, as well as others, it can be seen that the emphasis is on the adjustable means and not on the point of contact with the floor. In general, all such cross member supports in the prior art utilize a glide in view of its strength, but take along with that asset, the problem of the glides lack of mobility, particularly when moved along a carpeted floor.
A further alternative is with the use of a caster cup that is generally cup shaped that is slid underneath a roller of a caster assemble to aid in slowing the mobility of the caster and to stabilize the piece of furniture, particularly when used on a slippery flooring surface. The caster cups, however, are easily displaced from under the roller since they are not firmly locked to or attached to the caster assemblies and are thus difficult to maintain in place when the furniture is moved during the normal use of the furniture. Thus, over time, the caster cups become displaced with respect to the roller and no longer serve their intended purpose.
Accordingly, it would be advantageous to have a caster assemble that combines the strength and stability of the glide assembly with the mobility of the caster assembly. It would be further advantageous to have a support assembly that eliminates the swivel movement of the caster assembly to allow movement of the furniture to achieve the desirable strength of a glide assembly but additionally have mobility.
In addition, the supplier of casters assemblies and glide assemblies has to make and supply both types of assemblies i.e. caster assemblies and glide assemblies to insure that the customer can have the right assembly for the particular location. It would, obviously be advantageous to be able to use only one assembly and to have that assembly operate as both a glide and a caster assembly at the option of the user so that the user can easily convert the caster assembly to the glide function without the need for special tools or cumbersome methods of carrying out such conversion.